In a for loop, particularly in programming languages like Python, the fields that are optional include the initialization, condition, and increment/decrement expressions. For instance, in Python, you can create a loop using just the for
keyword followed by an iterable, omitting the traditional initialization and increment parts found in languages like C or Java. Additionally, in some languages, such as JavaScript, the loop can be constructed in a way that skips certain parts, leading to variations in syntax and functionality.
The do..while() loop tests the condition at the end of the loop. Therefore the loop body executes at least once. The while() loop (without do) tests the condition before entering the loop and before each iteration of the loop. The for() loop conditional expression is optional but, when specified, is tested before entering the loop and before each iteration of the loop.
The only loop that does not require an entry condition is the procedural goto loop: again: /*...*/ goto again; Although a do-while loop has no entry condition per-se, it still requires a mandatory entry condition into the second and all subsequent iterations. do { /*...*/} while (true); // mandatory entry condition into all but the 1st iteration And although a for loop's condition is optional, it is implicit: for (;;) {/*..*/} // implicit for ever loop for (;true;) {/*...*/} // explicit for ever loop
ditioFor loops are a little more complex then the While loop. A for loop as 3 optional parameters. They are the initializer list, the conditional check, and the post incrementer list. The initializer list is the section that you declare variables and/or initialize them to a specific value. The conditional check is the conditional check for the loop to continue or finish. The post incrementer list is a section that is used to apply post loop code. Once each iteration of the loop is complete, these lines of code are called to update variables or conditions. Then the loop runs againns. Then the loop runs again
For loops in C++ consist of three parts, all of which are optional. Each part is separated by a semi-colon, which is not optional, and each part may include multiple statements, separated by commas. The first portion is the initial expression, which can be used to both declare and initialise variables used within the loop. If variables are declared, they are local to the loop and fall from scope when the loop ends. The second portion is the conditional expression that is executed at the end of each iteration of the loop. If the expression evaluates false, the loop terminates. This is typically used to evaluate the variables initialised by the initial expression. The final portion is the end loop expression, which is executed at the end of each iteration prior to the conditional expression being evaluated. This is typically used to increment or decrement variables initialised in the initial expression. Within the body of a loop, jump statements can be used to exit the loop regardless of the conditional expression, or start a new iteration before executing any remaining commands within the loop. Jump statements include break, continue, goto and return, and are typically used in conjunction with a conditional expression. An infinite for loop has the following from: for(;;) { // The body of the loop must evaluate a conditional expression to allow // the loop to terminate via a jump statement. } A for loop that repeats 10 times can be expressed as: for(int x=0; x<10; ++x) { // Variable x will fall from scope when the loop ends. } The loop can also be expressed as an infinite loop: int x=0; for(;;) { if( ++x == 10 ) break; } // x is still in scope at this point, and has the value 10. Most for loops can also be written using while() loops, however variables used by the conditional expression must be declared outwith the loop, and will remain in scope when the loop terminates. int x=0; while(x++<10) { // First time around, x will be 1. } // x is still in scope at this point, and will have the value 11.
A while loop evaluates a conditional expression at the start of each iteration. If the conditional expression evaluates false, execution passes to the statement that immediately follows the body of the loop. If the conditional expression evaluates true, the body of the loop executes one iteration. When the end of the loop is reached, or a continue statement is encountered within the body of the loop, control passes back to the while statement where the conditional expression is re-evaluated. If a break statement is encountered within the body of the loop, the loop terminates and control passes to the next statement. If a return statement is encountered within the body of the loop, the loop terminates and control passes to the calling function.while (expression) {// repeats until the expression evaluates false}The braces are optional when the body of the loop is a simple statement. Compound statements must be enclosed in braces.A flag-controlled while loop has a simple conditional expression that evaluates a Boolean value:bool x;// ...while (x==true) { // flag-controlled loop// ...}}The above loop can also be written without the equality operator:while (x) { // flag-controlled loop // ...}Moreover, any integral type (such as int or char) will implicitly convert to a bool such that non-zero values evaluate true and zero evaluates false. As such, any integral type can be used in a flag-controlled loop.
for (<exp1>; <exp2>; <exp3>) <statement> exp1 and exp3 are optional; statement can be null-statement or block-statement. Correction: All expressions are optional. An infinite loop has no expressions: for(;;);
The do..while() loop tests the condition at the end of the loop. Therefore the loop body executes at least once. The while() loop (without do) tests the condition before entering the loop and before each iteration of the loop. The for() loop conditional expression is optional but, when specified, is tested before entering the loop and before each iteration of the loop.
In terms of performance there is no difference whatsoever. Which version you use is usually decided by which is more appropriate for the type of loop you want to execute. for() loops allow you to combine an initial condition, a conditional expression and a loop expression in a single statement. The initial condition can include a declaration which falls from scope when the loop ends, but all expressions are optional. If a conditional expression is not declared, a conditional expression must appear in the body of the loop. while() loops are similar to for() loops, but are generally used when an initial condition and loop expression are not required, but a condition is. The condition is non-optional. do..while() loops are used when a loop must execute at least once, and a condition is not optional.
Required, Optional, Default, Conditional, and Selection
Required, Optional, Default, Conditional, and Selection
Required, Optional, Default, Conditional, and Selection
Magnetic fields flow from north to south in a continuous loop, with the lines of force moving outward from the north pole and curving back towards the south pole. This creates a closed loop pattern that allows the magnetic field to circulate and interact with other magnetic fields.
You use a break statement to end execution of the enclosing iterator (loop) or switch statement. If omitted at the end of a case label, execution continues to the next case label, including the default case, until a jump statement is encountered (break, goto or return) or the switch statement falls from scope. Sometimes this can be desirable behaviour, thus the use of break is optional. A break statement is always optional at the end of the default case, or the last case label. Its usage in loops is always optional, to allow a loop to end prematurely regardless of the conditional expression that controls the loop.
The only loop that does not require an entry condition is the procedural goto loop: again: /*...*/ goto again; Although a do-while loop has no entry condition per-se, it still requires a mandatory entry condition into the second and all subsequent iterations. do { /*...*/} while (true); // mandatory entry condition into all but the 1st iteration And although a for loop's condition is optional, it is implicit: for (;;) {/*..*/} // implicit for ever loop for (;true;) {/*...*/} // explicit for ever loop
There are seven fields in the password file on each line for each user. They are: login name · optional encrypted password · numerical user ID · numerical group ID · user name or comment field · user home directory · optional user command interpreter
To iterate the same command or series of commands while a conditional expression remains true. The parameters of those commands can (optionally) be altered by each iteration of the loop, as can the parameters used in the conditional expression.Conditional expressions may also be evaluated anywhere within the loop, forcing the loop to continue (start a new iteration, skipping any remaining commands in the loop), break (exit the loop completely and begin execution at the first command following the loop) or goto (jump to a specified label either inside or outside of the loop).The for() loop is the most common type of loop, usually used for counting a series of values in a sequence of increments. It accepts three parameters: the start value, a conditional expression and a function. All parameters are optional, but if a conditional expression is specified it is evaluated at the end of each loop, immediately after invoking the optional command.The while() loop must specify a conditional expression which is evaluated before each iteration of the loop.The do...while() loop must also specify a conditional expression which is evaluated at the end of each iteration. Such loops are guaranteed to loop at least once.All three are capable of creating infinite loops. Often this is desirable, but great care must be taken to ensure an infinite loop can exit gracefully at some point, otherwise your program will stall. The worst-case scenario is that the loop could bring the entire system to a halt either because the loop continually allocates memory or makes recursive calls to the function containing the loop. Infinite loop must therefore contain a conditional expression to exit the loop from within the body of the loop itself.
ditioFor loops are a little more complex then the While loop. A for loop as 3 optional parameters. They are the initializer list, the conditional check, and the post incrementer list. The initializer list is the section that you declare variables and/or initialize them to a specific value. The conditional check is the conditional check for the loop to continue or finish. The post incrementer list is a section that is used to apply post loop code. Once each iteration of the loop is complete, these lines of code are called to update variables or conditions. Then the loop runs againns. Then the loop runs again